1. Field of the Invention
This invention relates, generally, to anti-theft devices. More particularly, it relates to a device that locks an extended hydraulic cylinder so that it cannot move.
2. Description of the Prior Art
Heavy machinery such as such as loaders, backhoes, skid steer loaders, crawlers, graders, articulated loaders, trenchers, dozers, and the like are typically parked on the job site throughout the course of a construction project because the effort to transport the equipment to a secure site is expensive and time-consuming. The machinery is susceptible to theft and vandalism.
Equipment theft from construction sites is a significant problem. The machinery is expensive to replace if stolen.
Devices that lock steering wheels offer little protection because such devices are easily cut off with a hacksaw or other suitable cutting tool. Other locking devices can be burned or pried off.
What is needed, then, is a locking device that is highly resistant to sawing, burning, or prying.
Buckets, blades and other attachments of heavy machinery commonly include hydraulic cylinder and piston rod assemblies. Hydraulic pressure is harnessed to retract and extend a piston rod from a hydraulic cylinder.
A steel sleeve is commonly interposed between the connection point, or bearing, at the distal end of the piston rod and the cylinder. The steel sleeve prevents retraction of the piston rod in the event of loss of hydraulic pressure, thereby preventing unintended movement of the attachment.
A steel sleeve can also be used as a locking device by placing it over the exposed piston rod. A padlock is typically employed to lock the sleeve. This prevents the sleeve from being removed and thus secures the piston rod in an extended condition.
With the rod in an extended position the attachments are secured in either a lowered or raised position, thereby hindering unauthorized movement of the heavy machinery.
Prior art hydraulic locking devices include U.S. Pat. No. 4,373,851 to Confoey that discloses a split cylindrical sleeve that encloses around the piston rod and includes extended tabs that are locked together using a padlock to prevent removal. The Confoey configuration is susceptible to having the padlock cut off using bolt cutters or broken off using extreme force.
An improved locking device that is easy to install and remove, which is durable, and which protects against theft and vandalism is needed.
However, in view of the prior art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how the identified needs could be fulfilled.